Adjustable latch for a relay

ABSTRACT

A magnetic latch for use with relay is provided. In one embodiment of the invention, a latch which can be assembled to a standard relay in the field is provided for latching the relay in a predetermined position. The latch is magnetically biased toward a latching position to follow the movement of the movable contact in the relay and to latch the relay when in the selected position. A spring can be added to bias the latch towards a latching position. The movable contacts of a standard relay are spring biased by a force which is less than that provided by the disclosed magnetic latch. An electric coil is provided for opposing the magnetic flux generated in the latch permitting the spring provided in the standard relay to move the magnetic latch to an unlatched position. In a second embodiment of the invention a magnetic latch for a relay is provided which is latched by a permanent magnet in the open or closed position. The latch includes an armature which is held in the open or closed position by means of two permanent magnets. A coil disposed around the armature can be energized to change the position of the magnetic latch. The direction of movement of the armature is determined by the direction of current flow through the coil and this is controlled by a diode switching arrangement.

United States Patent [1 1 Johnston et al.

fill] 3,886,507

[ May 27, 1975 I54] ADJUSTABLE MAGNETIC LATCH FOR A RELAY [75]Inventors: Robert J. Johnston; Alfred E. Maier,

both of Beaver Falls, Pa.

[73] Assignee: Westinghouse Electric Corp.,

Pittsburgh, Pa.

221 Filed: Oct. 5, 1973 21 Appl. No.: 404,058

Primary E.raminer-G. Harris Attorney. Agent, or FirmHv G. Massung [57]ABSTRACT A magnetic latch for use with relay is provided. In oneembodiment of the invention, a latch which can be assembled to astandard relay in the field is provided for latching the relay in apredetermined position. The latch is magnetically biased toward alatching position to follow the movement of the movable contact in therelay and to latch the relay when in the selected position. A spring canbe added to bias the latch towards a latching position, The movablecontacts of a standard relay are spring biased by a force which is lessthan that provided by the disclosed magnetic latch. An electric coil isprovided for opposing the magnetic flux generated in the latchpermitting the spring provided in the standard relay to move themagnetic latch to an unlatched position. in a second embodiment of theinvention a magnetic latch for a relay is provided which is latched by apermanent magnet in the open or closed position. The latch includes anarmature which is held in the open or closed position by means of twopermanent magnets. A coil disposed around the armature can be energizedto change the position of the magnetic latch. The direction of movementof the armature is determined by the direction of current flow throughthe coil and this is controlled by a diode switching arrangement.

7 Claims, 5 Drawing Figures PATENTEDMY 2 7 ms SHEET FlG.2

PATENTEU MAY 2 7 I975 SHEET PATENTEDMAYEY I975 SHEET 3 3,886,507

FIG.4

ADJUSTABLE MAGNETIC LATCH FOR A RELAY BACKGROUND OF THE INVENTION Thisinvention is related to a magnetic latch for use with an electric relay.More particularly, this invention is concerned with a magnetic latchutilizing permanent magnets to seal the latch in a predeterminedposition and an electric coil to overcome the magnetic flux generated bythe permanent magnets permitting the latch to change positions.

Standard low voltage relays require a latch which can follow therectilinear motion of their operator. It is desirable that the positionof the latch be capable of being rapidly switched. Rapid switchingoperation has been a problem with prior art relay latches. Forstandardization and field assembly applications, it is desirable thatthe magnetic latch be adiustable to fit a variety of standard relays. Insome applications it is desirable that the magnetic latch sense theposition of the movable contacts in the standard relay and latch in thedesired position. it is also desirable that the latch be of a simplereliable construction having a minimum number of parts.

SUMMARY OF THE INVENTION In one embodiment of the invention a latch foruse with an electric relay is provided having a housing formed of amagnetizable or ferromagnetic material with a core formed also of aferromagnetic material being disposed within the housing. The core ismovable between a latched position in contact with the housing and anunlatched position where the core does not contact the housing. Thepermanent magnet is disposed Within the housing between the housing andthe core so as to form a magnetic circuit through the core and housingwhen the core is in contact with the housing. This magnetic circuitsecurely latches the core to the housing. The permanent magnets bias thecore toward a latched position in contact with the housing. A spring mayalso be provided to aid in biasing the core towards a latched positionin contact with the housing. An electric coil which when energizedopposes the flux generated by the permanent magnet is disposed around aportion of the core. When the electric coil is energized, the core isfreed from contact with the housing and can be moved to the unlatchedposition. This latch is particularly adaptable for use on a standardrelay consisting of a series of moving and stationary contacts in whichthe position of the moving contacts are controlled by a spring loadedcross bar which is moved electromechanically to the open or closedposition. The disclosed magnetic latch is provided with a latch armwhich extends from the core and can follow the movement of the springloaded cross bar used in the standard relay. When the standard relaymoves to a position where the core of the magnetic latch contacts thehousing, the magnetic latch latches and the standard relay is held inthis position. When the coil is energized, the force of the permanentmagnets is bucked and the core will move due to the force generated bythe cross bar return spring provided in a standard relay.

The core has a threaded opening formed therein which is engaged by athreaded portion provided on the latch arm. Thus, the length of thelatch arm can be adjusted by threading the latch arm in or out. Anextension can be provided on the latch arm which can be rotated toadjust the length of the latch arm. The disclosed magnetic latch iscapable of rapid operation. The disclosed latch also has a low powerconsumption in that only a short current pulse is required to unlatchthe disclosed magnetic latch.

In another embodiment of this invention, a magnetic latching relay isprovided. In this embodiment, the movable contacts of the relay arelatched by permanent magnets in the open position and in the closedposition. A movable core is supported for rectilinear motion inside aferromagnetic housing. The movable contacts of the relay are connectedto the core to change positions in response to core movement. The coreis held in the open or closed position by permanent magnets which aredisposed in the housing between a portion of the core and the housing. Acoil is wrapped around the core and movement of the core between theopen and closed position is accomplished by applying current, of theproper polarity, to the coil. The direction of throw of the coil isdictated by the direction of the current flow through the coil. A pairof diodes serving as a directional switch are provided to select thedirection of current flow and thus determine the direction of movementof the core, coil and contact assembly. When the coil is not energized,the core is sealed in either the open or closed position by thepermanent magnets.

It is an object of this invention to provide a magnetic latch for usewith an electric relay which is capable of rapid repeated operation.

It is a further object of this invention to provide a magnetic latch ofa simple rugged construction which is adjustable to be mounted on avariety of standard relay configurations.

A still further object of this invention is to provide a latch which canbe sealed in position by permanent magnets and which requires a smallamount of energy for release.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of theinvention, reference may be had to the preferred embodiments exemplaryof the invention shown in the accompanying drawings, in which:

FIG. I is a top view of a magnetic latch utilizing a teaching of thepresent invention with portions broken away for clarity;

FIG. 2 is a side sectional view of the magnetic latch shown in FIG. 1 inthe latched position;

FIG. 3 is a view similar to FIG. 2 with the magnetic latch in theunlatched position;

FIG. 4 is a side sectional view of a relay utilizing another embodimentof the invention; and

FIG. 5 is a view similar to FIG. 4 with the relay in the open position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawingsand FIGS. 1, 2 and 3 in particular, there is shown a magnetic latch 10utilizing the teaching of the present invention. The magnetic latch 10comprises a core 12 which is supported for movement along itslongitudinal axis and a housing 14 which partially surrounds the core12. The core 12 and the housing 14 are both constructed from aferromagnetic material. A pair of permanent magnets 16 are disposedwithin housing 14. Permanent magnets 16 are disposed with one pole,formed along side 15, facing housing 22 and the other pole, formed alongside 17,

facing core 12. The poles formed along side 17 facing core 12 are of thesame polarityeither both north poles or both south poles. When magneticlatch is in the latched position as seen in FIG. 2, the permanentmagnets 16 set up a magnetic flux path through magne tizableferromagnetic core 12 and magnetizable housing 14, to securely hold core12 to housing 14. An electric coil 18 is provided surrounding a portionof core 12. Electric coil 18 when energized generates magnetic fluxthrough core 12 in opposition to the magnetic flux provided by permanentmagnet 16. This permits the magnetic latch 10 to be moved to theunlatched positron.

Housing 14 has a generally U-shaped configuration with two leg portions20 and 22 and a bight portion 24 connecting leg portions 20 and 22. Anopening 26 is provided through bight portion 24. A portion of latch arm28 extends through the opening 26 formed in bight portion 24. Themagnetic latch 10 can be connected to a standard relay 50, a portion ofwhich is schematically indicated with phantom lines. Standard relay 50includes a set of stationary contacts 52, a pair of movable contacts 54which engage stationary contacts 52 and a bridging member 56 whichsupport contacts 54. Bridging member 56 is connected to an insulatingcross bar 58. Cross bar 58 is spring biased by spring 60 toward an openposition. Standard relay 50 can be closed by an electromechanicaloperator (not shown). When standard relay 50 moves to the closedposition as shown in FIG. 2, latch arm 28 follows the movement of crossbar 58 so that when contacts 52 and 54 engage magnetic latch 10 issealed with core 12 in engagement with housing 14. The force with whichpermanent magnets 16 latch core 12 to housing 14 is greater than theforce provided by cross bar biasing spring 60 and the standard relay 50is thus held in the closed position. When coil 18 is energized, theforce of magnets 16 is bucked and the core 12 will now move up due tothe dominant force generated by the cross bar return spring 60.

Latch arm 28 is provided with a threaded portion 30 which engages athreaded portion 32 of core 12. The threaded engagement between core 12and latch arm 28 permits the distance which latch arm 28 extends fromthe bight portion 24 of housing 14 to be adjusted. This allows magneticlatch 10 to be used with various standard relays 50 which requiredifferent lengths of operating arm 28.

A top cover plate 40 having an opening 42 formed therein is provided.Cover plate 40 is formed from a non-magnetic material such as brass oran electric insulator. Cover plate 40 is secured to flange portion 44extending from housing 14. Screws 46 can be used to secure cover plate40 to housing 14. A spring 34 seated at one end against cover plate 40and at the other end against core 12 may be provided to urge core 12toward the latched position. Since cover plate 40 is made from anon-magnetic material, permanent magnets 16 will generate a forcecomponent in core 12 urging core 12 toward the latched position.Permanent magnets 16 give a force in the downward direction and a smallbiasing spring 34 is not necessary when latch 10 is new but afterseveral million operations due to wear it may be desirable to have abiasing spring 34 to assure that core 12 will rapidly and accuratelyfollow cross bar 58. Coil 18 is wound on a spool 36 having a generallyrectangular-shaped passage 38 extending therethrough. Core 12 has agenerally rectangular outer periphery of a size slightly smaller thanthe rectangular opening 38 through spool 36. When the magnetic latch 10is thus assembled, with a portion of core 12 extending into therectangular passage 38 through spool 36, core 12 is effectively heldagainst rotary motion with respect to housing 14. An extension 61 isconnected to the threaded portion 30 of lever arm 28 and extends throughopening 42 formed in end plate 40. The distance which latch arm 28extends from the housing 14 can thus be varied by rotating extension 61.A slot 62 is provided in extension 61 for easy adjustment of latch arm28. This adjustability feature permits the magnetic latch 10 to be usedwith a variety of standard relays 50. Magnetic latch 10 requires a smallamount of power for operation. The operating speed of magnetic latch 10is very rapid. Magnetic latch 10 has been experimentally verified tohave an operating speed of over 180 operations per minute. Extension 61permits magnetic latch 10 to be manually latched or unlatched. Theforces generated by permanemt magnets 16 and electric coil 18 whenenergized are equal and in opposition. Cross bar biasing spring 60 thenmoves core 12 to the unlatchecl position. Core 12 is biased by magneticflux and in some cases spring 34 to follow and sense the position ofcontacts 54 and 52. Two magnets 16 and 18 set up two separate magneticloops through a single pole core 12. The hold strength of the disclosedmagnetic latch 10 is a function of a variable air gap. This helpsmagnetic latch 10 to achieve a far superior operating speed uponunlatching than that of the prior art. Tests have shown this magneticlatch 10 to accomplish an excess of 180 latches and unlatches perminute.

Referring now to FIGS. 4 and 5, there is shown a latching relayillustrating another embodiment of this invention. A movable core 72 isdisposed within a housing 74. Movable core 72 is movable along itslongitudinal axis between a latch closed position shown in FIG. 4 and alatched open position shown in FIG. 5. Movable core 72 and housing 74are formed from ferromagnetic or magnetizable material. A spool 76formed from a non-magnetizable material partially surrounds the core 72.Core 72 is held in the open or closed position by permanent magnet 78.Permanent magnet 78 forms a magnetic path through core 72 and housing 74to latch core 72 in the open or closed positions. A coil 80 is woundaround spool 76. Movement of core 72 from the open to the closedposition or vice versa may be accomplished by application of power tocoil 80. Core 72 is connected to a bridging member 156 made ofnon-magnetic material which supports movable contacts 54. The bridgingmember 156 thus completes a circuit between movable contacts S4. in theclosed position movable contacts 54 engage stationary contacts 52.Diodes 82 and 84 are provided for selecting the direciton of currentflow through coil 80. The direction of the throw caused by coil 80 willbe dictated by the direction of current flow through coil 80. The forcegenerated by coil 80 when energized overcomes the force due to permanentmagnet 78 and switches the position of core 72. Core 72 is then latchedin the switched position by permanent magnet 78. Direction of currentflow, through coil 80, as permitted by diode 82 or 84 will determine theposition of core 72. An extension 88 of nonmagnetic material is providedextending from core 72 to permit manual operation of relay 70. Relay 70is constructed for rapid switching operations.

We claim:

1. A latch comprising:

a housing formed of a magnetizable material;

an elongated core formed of a magnetizable material disposed within saidhousing and being movable between a latched position wherein said coreis in contact with said housing and an unlatched position wherein saidcore is not in contact with said housing;

a magnet disposed within said housing between said housing and said coreso as to form a magnetic circuit through said core and said housing whensaid core is in contact with said housing to securely hold said core tosaid housing;

said magnet disposed with the north-south pole of said magnet alignedsubstantially perpendicular to the longitudinal axis of said core;

biasing means for biasing said core towards the latched position;

an electric coil, disposed in said housing, which when energized opposesthe magnetic circuit formed through said core by said magnet permittingsaid core to be moved to the unlatched position;

said housing has a generally U-shaped cross-section with a bight portionconnecting the two legs of said U-shaped housing;

said core disposed within said housing for movement along itslongitudinal axis between a latched position in engagement with thebight portion of said U-shaped housing and an unlatched position spacedfrom the bight portion of said U-shaped housing;

an end plate formed from non-magnetic material connecting the free endsof the legs of said U- shaped housing;

said housing having an opening formed in the bight portion;

a latch arm extending from said core through the opening in the bightportion of said housing;

said latch arm being secured to said core to move in unison with saidcore;

said core having a longitudinal threaded opening formed therein; and

said latch arm includes a threaded portion which engages the threadedopening formed in said core so that the distance which said latch armextends from said latch can be varied.

2. A latch comprising:

a housing formed of a magnetizable material;

an elongated core formed of a magnetizable material disposed within saidhousing and being movable between a latched position wherein said coreis in contact with said housing and an unlatched position wherein saidcore is not in contact with said housing;

a magnet disposed within said housing between said housing and said coreso as to form a magnetic circuit through said core and said housing whensaid core is in contact with said housing to securely hold said core tosaid housing;

said magnet disposed with the north-south pole of said magnet alignedsubstantially perpendicular to the longitudinal axis of said core;

biasing means for biasing said core towards the latched position;

an electric coil, disposed in said housing, which when energized opposesthe magnetic circuit formed through said core by said magnet permittingsaid core to be moved to the unlatched position;

said housing has a generally U-shaped cross-section with a bight portionconnecting the two legs of said U-shaped housing;

said core disposed within said housing for movement along itslongitudinal axis between a latched position in engagement with thebight portion of said U-shaped housing and an unlatched position spacedfrom the bight portion of said U-shaped housing;

an end plate formed from non-magnetic material connecting the free endsof the legs of said U- shaped housing;

said housing having an opening formed in the bight portion;

a latch arm extending from said core through the opening in the bightportion of said housing;

said latch arm being secured to said core to move in unison with saidcore;

said core having a threaded longitudinal opening formed therethrough;

said end plate having an opening formed therein;

said latch arm includes a threaded portion which engages the threadedopening formed in said core so that the distance which said latch armextends from said latch can be varied; and,

an extension extending from the threaded portion of said latch armthrough the opening in said end plate whereby the distance which saidlatch arm extends from said latch can be varied by rotating saidextension.

3. A latch as claimed in claim 2 wherein:

said electric coil surrounds a portion of said core.

4. A latch as claimed in claim 3 including:

a spool having a generally rectangular opening therethrough around whichsaid coil is wound;

said core having a generally rectangular cross-section which fits in thegenerally rectangular opening in said spool to prevent relativerotational movement of said core with respect to said spool; and,

said spool is fixed with respect to said housing.

5. A latch as claimed in claim 4 wherein:

said spring is of the coil variety and is disposed around saidextension; and,

said magnet is of a flat rectangular shape.

6. A latch comprising:

an elongated core formed from a ferromagnetic material and being movablebetween a latched and an unlatched position;

biasing means urging said core towards the latched position;

magnetic sealing means, comprising a flat rectangular permanent magnetdisposed with the northsouth magnetic axis perpendicular to thelongitudinal axis of said core, to form a magnetic flux path throughsaid core when said core is in the latched position to magneticallyretain the latch in the latched position;

an electric coil disposed so as to buck the magnetic flux path in saidcore formed by said magnetic sealing means when energized allowing saidcore to be moved to the unlatched position;

a housing having a generally U-shaped cross section formed from aferromagnetic material and contain 7 i 8 ing said core and said magneticsealing means said latch arm is threadably secured to said core; and,Wl'lhln the confines defined y Sald housmgl an extension rigidly securedto said latch arm and exsaid coil disposed around a portion of said coreand being fixed relative to said housing; and,

a latch arm adjustably secured to said core and exi tending from saidhousing. mtatmg Said extension- 7. A latch as claimed in claim 6wherein:

tending from said housing so that the distance said latch arm extendsfrom said latch can be varied by

1. A latch comprising: a housing formed of a magnetizable material; anelongated core formed of a magnetizable material disposed within saidhousing and being movable between a latched position wherein said coreis in contact with said housing and an unlatched position wherein saidcore is not in contact with said housing; a magnet disposed within saidhousing between said housing and said core so as to form a magneticcircuit through said core and said housing when said core is in contactwith said housing to securely hold said core to said housing; saidmagnet disposed with the north-south pole of said magnet alignedsubstantially perpendicular to the longitudinal axis of said core;biasing means for biasing said core towards the latched position; anelectric coil, disposed in said housing, which when energized opposesthe magnetic circuit formed through said core by said magnet permittingsaid core to be moved to the unlatched position; said housing has agenerally U-shaped cross-section with a bight portion connecting the twolegs of said U-shaped housing; said core disposed within said housingfor movement along its longitudinal axis between a latched position inengagement with the bight portion of said U-shaped housing and anunlatched position spaced from the bight portion of said U-shapedhousing; an end plate formed from non-magnetic material connecting thefree ends of the legs of said U-shaped housing; said housing having anopening formed in the bight portion; a latch arm extending from saidcore through the opening in the bight portion of said housing; saidlatch arm being secured to said core to move in unison with said core;said core having a longitudinal threaded opening formed therein; andsaid latch arm includes a threaded portion which engages the threadedopening formed in said core so that the distance which said latch armextends from said latch can be varied.
 2. A latch comprising: a housingformed of a magnetizable material; an elongated core formed of amagnetizable material disposed within said housing and being movablebetween a latched position wherein said core is in contact with saidhousing and an unlatched position wherein said core is not in contactwith said housing; a magnet disposed within said housing between saidhousing and said core so as to form a magnetic circuit through said coreand said housing when said core is in contact with said housing tosecurely hold said core to said housing; said magnet disposed with thenorth-south pole of said magnet aligned substantially perpendicular tothe longitudinal axis of said core; biasing means for biasing said coretowards the latched position; an electric coil, disposed in saidhousing, which when energized opposes the magnetic circuit formedthrough said core by said magnet permitting said core to be moved to theunlatched position; said housing has a generally U-shaped cross-sectionwith a bight portion connecting the two legs of said U-shaped housing;said core disposed within said housing for movement along itslongitudinal axis between a latched position in engagement with thebight portion of said U-shaped housing and an unlatched position spacedfrom the bight portion of said U-shaped housing; an end plate formedfrom non-magnetic material connecting the free ends of the legs of saidU-shaped housing; said housing having an opening formed in the bightportion; a latch arm extending from said core through the opening in thebight portion of said housing; said latch arm being secured to said coreto move in unison with said core; said core having a threadedlongitudinal opening formed therethrough; said end plate having anopening formed therein; said latch arm includes a threaded portion whichengages the threaded opening formed in said core so that the distancewhich said latch arm extends from said latch can be varied; and, anextension extending from the threaded portion of said latch arm throughthe opening in said end plate whereby the distance which said latch armextends from said latch can be varied by rotating said extension.
 3. Alatch as claimed in claim 2 wherein: said electric coil surrounds aportion of said core.
 4. A latch as claimed in claim 3 including: aspool having a generally rectangular opening therethrough around whichsaid coil is wound; SAID core having a generally rectangularcross-section which fits in the generally rectangular opening in saidspool to prevent relative rotational movement of said core with respectto said spool; and, said spool is fixed with respect to said housing. 5.A latch as claimed in claim 4 wherein: said spring is of the coilvariety and is disposed around said extension; and, said magnet is of aflat rectangular shape.
 6. A latch comprising: an elongated core formedfrom a ferromagnetic material and being movable between a latched and anunlatched position; biasing means urging said core towards the latchedposition; magnetic sealing means, comprising a flat rectangularpermanent magnet disposed with the north-south magnetic axisperpendicular to the longitudinal axis of said core, to form a magneticflux path through said core when said core is in the latched position tomagnetically retain the latch in the latched position; an electric coildisposed so as to buck the magnetic flux path in said core formed bysaid magnetic sealing means when energized allowing said core to bemoved to the unlatched position; a housing having a generally U-shapedcross section formed from a ferromagnetic material and containing saidcore and said magnetic sealing means within the confines defined by saidhousing; said coil disposed around a portion of said core and beingfixed relative to said housing; and, a latch arm adjustably secured tosaid core and extending from said housing.
 7. A latch as claimed inclaim 6 wherein: said latch arm is threadably secured to said core; and,an extension rigidly secured to said latch arm and extending from saidhousing so that the distance said latch arm extends from said latch canbe varied by rotating said extension.